Various techniques are known from the past for measuring the diameter of disk body such as coins tokens and the like. These include:
1) The use of a potted core for detecting the influence of the coin on a magnetic filed, (detecting oscillations of a magnetic field). Such arrangements can be devised and calibrated to judge the diameter of the coin from the data which the arrangement provides; PA1 2) The use of light detecting arrangements for detecting the quantity of the light which is interrupted by the disk body to measure the diameter of such disk body; PA1 3) The use of a moving arm toward a diameter direction of disk body, and measuring the diameter according to the movement quantity thereof. Such an arm movement apparatus which moves an arm to a diameter direction of disk body and measures the diameter in the movement quantity thereof is concretely disclosed in the specification of Japanese Patent Disclosure 5-45104.
This disclosed apparatus makes a measurement member touch the circumference edge of the coin which moves along the reference surface. Then, this apparatus converts the rotated angle of the measurement member into a change of the resistance value through a gear apparatus and measures the diameter of the moved coin depending on a changed pattern with this resistance value.
However, in the above mentioned way of measuring a diameter of disk body, there is a problem of the requirement for substantial installation space of the measurement apparatus, or the need to provide a distance of the natural fall of the disk body such as the coin, etc.